Canon EF - Manual (Page 21)

В Variable Aperture AE Control
Method
Commonly known as "shutter priority EE," the
Variable Aperture AE control method gives the
photographer absolute control over the shutter speed
to prevent camera shake. You select a shutter speed
appropriate to the action and/or the lens you are
using, and the camera automatically adjusts the
aperture of the lens to precisely the proper f/stop or
fraction thereof.
C
Silicon Photocell
The Silicon Photocell is a highly accurate and
extremely stable light measuring cell having a wider
range of sensitivity and much faster response to
rapidly changing light levels than the conventional
CdS cell. At ASA 100, the metering range of the
Silicon Photocell is from EV18 (1/1000 sec. atf/16)
down to EV —2 (8 sec. at f/1.4), which is five f/stops
more sensitive than the normal CdS cell. At ASA 25,
the range is from 1/1000 sec. at f/8 down to 30 sec.
at f/1.4. This increased sensitivity range is made
possible by the development of a special logarithmic
amplifier to intensify the low amount of current
generated by the photocell in very dim light
conditions.